In recent years, attention has been paid to a technique of comprising a TFT by using a semiconductor thin film (thickness of around several to several hundreds nm) formed over a substrate having an insulating surface. A TFT is widely applied to an electronics device such as an IC or an electro-optical device, and is under development especially as a switching element or a driver circuit of a display device.
Although a glass substrate or quartz substrate is often used in the display device, it is easily broken and heavy, which are defects. Therefore, a glass substrate or quarts substrate is difficult to enlarge in a mass production. Hence, forming a TFT element on a substrate with flexibility, typically, on a flexible plastic film is attempted.
However, when a high-performance polycrystalline silicon film is used for an active layer of a TFT a high temperature process of several hundred degrees Celsius is necessary in a manufacturing process; thereby it can not be directly formed on a plastic film.
Therefore, a method for peeling a peel-off layer existing on a substrate through a separating layer from the substrate is proposed. For example, it is a method for providing a separating layer comprising amorphous silicon, a semiconductor, nitride ceramics or organic polymer, then to radiate laser light through a substrate to generate a peeling in layer in the separating layer, followed by separating the substrate. (see the patent document 1). Additionally, there is also a description that a liquid crystal display device is completed by pasting a peel-off layer (referred to as a layer to be transferred in the gazette) to a plastic film using the technique (see the patent document 2). In addition, when articles regarding a flexible display are looked, technologies of each company are introduced. (see the non-patent document 1).
Patent Document 1
Unexaminined Patent Publication No. 10-125929 gazette
Patent Document 2
Unexamined Patent Publication No. 10-125930 gazette
Non-Patent Document 1
Nikkei Microdevice, Nikkei BP, No. Jul. 1, 2002, Jul. 1, 2002, pages 71 to 72